Sensory, chemical and microbiological assessment of farm-raised European sea bass (Dicentrarchus labrax) stored in melting ice

Farm raised European sea bass ( Dicentrarchus labrax ) were stored in melting ice for a period up to 22 days from the time of harvest, and sensory, chemical, and microbiological assessments were made at intervals. The storage life of the ungutted fish, determined by sensory evaluation of the cooked flesh, was 19 days. Of the chemical tests, only k ₁ value provided a useful means of monitoring early storage change. Trimethylamine, total volatile bases and pH showed practically no change during the first half of the edible storage life of the fish. Changes in free fatty acid (FFA) content and thiobarbituric acid (TBA) value could not be used to determine loss of acceptability or end of storage life. Sulphide producing bacteria constituted a very low proportion of the total aerobic flora, suggesting that the common sulphide producer Shewanella putrefaciens was not a major spoiler of sea bass in this trial.     

Assessment of shelf-life of maricultured gilthead sea bream (Sparus aurata) stored in ice

Gilthead sea bream ( Sparus aurata ) were stored in melting ice (0 °C) for a period of 24 days from the time of harvest with sensory assessments of the whole raw fish and of the cooked fish flesh conducted at regular intervals. The ungutted fish was given an EC freshness grade E for up to 3 days, grade A for a further 7 days, and grade B for 4 more days after which it was graded as C (unfit). The sensory score for flavour of the cooked fillets decreased linearly with period of storage: fresh characteristic flavours were present for 2–4 days, decreasing to a relatively bland flavour after 10–12 days. Off flavours were evident by 13–15 days storage and by 18–19 days the flesh was unpalatable. With the possible exception of hypoxanthine, none of the chemicals investigated was particularly useful as an indicator of change. Changes in pH, trimethylamine and total volatile bases during the first half of the edible storage life were insignificant. Deterioration of flesh lipids, assessed by free fatty acid content and thiobarbituric acid value, appeared to present no serious problem during shelf-life. Proximate composition and sensory attributes, appropriate for routine inspection of gilthead sea bream were also determined.     

Storage of New Zealand Jack Mackerel (Trachurus novaezelandiae) In Ice: Chemical, Microbiological and Sensory Assessment

Physical, sensory, microbiological and chemical analyses were carried out on jack mackerel during 23 days of storage in ice. Sensory results indicate that jack mackerel used in this trial had a shelf-life of 7 days. Aerobic plate counts never exceeded 10⁶/g flesh during the first 11 days. The K value reached 20% after 7 days. Trimethylamine, total volatile base, pH and thiobarbituric acid analyses were not good indicators of changes in quality during the shelf-life. Proximate analyses were carried out on representative samples of the fish.     

A review of the kinetics of degradation of inosine monophosphate in some species of fish during chilled storage

A literature search was made for data on the concentrations of inosine monophosphate (IMP) and its degradation products, inosine (Ino) and hypoxanthine (Hx), in the flesh of vertebrate fish during storage in ice. Twenty‐one publications containing data for forty‐five species were selected for review. A mathematical model was developed for analysing the data by assuming that the kinetics of degradation of IMP could be modelled as consecutive first order reactions. The model was fitted to the data and in about half of the cases examined in the review the data suggested that IMP and degradation products were lost by leaching and the kinetic model was extended to allow for this loss. In all of the cases reviewed the mathematical model was a good fit to the experimental data and the reaction rates for the reactions are tabulated in the paper. In all species the concentration of IMP decreased as a first order reaction, but for thirteen of the species examined the enzyme model of IMP to Ino to Hx did not fit the data in that either Ino or Hx did not accumulate in the muscle. There were only a few examples of replications of storage trials within species and comparison of the outcomes of these replications suggested that season or, in the case of farmed fish, genetic stock or cultural practices might influence initial IMP concentrations or reaction rates.     

Changes in the flesh of cooked farmed salmon (Oncorhynchus kisutch) with previous storage in slurry ice (−1.5 °C)

Whole, farmed Coho salmon (Oncorhynchus kisutch) were sacrificed in slurry ice (−1.5 °C) then stored in this medium for further processing after 0, 5 and 9 days. They were cooked whole and the flesh was evaluated by sensory, physical and chemical techniques to establish if significant changes had occurred as a result of the storage period. Initial samples from harvest were also evaluated for comparison. There was evidence of increases in trimethylamine, lipid hydrolysis, lipid oxidation (anisidine and thiobarbituric acid values) and interaction compound formation (fluorescence and browning measurements). The fish structure became more breakable with longer storage but there were no changes in sensory assessments for rancid and putrid odours, so that scores were less than 0.5 on a 11-point scale. From the present results, primary and secondary lipid oxidation development and further interaction compound formation appear to be the main measurable indicators of quality changes in cooked Coho salmon. However, and according to sensory appreciation, slurry ice has shown to be a suitable medium for previous storage of Coho salmon for periods of up to 9 days.     

Gilthead seabream (Sparus aurata): suitability for freezing and commercial alternatives

The quality of portion‐size farmed gilthead seabream (Sparus aurata) during frozen storage and the influence of post‐mortem treatments were studied in order to find new ways of marketing this species. Portion‐sized gilthead seabream, fasted for 48 h prior to slaughter, were frozen and stored at ?20 °C for up to one year. Whole fish were frozen immediately after rigor mortis; gutted fish were frozen immediately after rigor and after 5 days of storage in ice. All lots were stored at ?20 °C for up to one year. The myofibrillar protein of this species was very stable and a slight decrease of solubility in salt solutions was found only after one year of frozen storage. A slight decrease in water‐holding capacity and a slight increase in shear strength were observed, but these were lower than in other species. These changes were reflected as increased toughness and reduced juiciness in sensory analysis of the cooked fillets after one year. The main changes in the cooked fillets were observed in odour and flavour. No significant detrimental effect due to the guts was detected during frozen storage. Storage in ice prior to freezing was reflected in sensory assessment of the raw fish, mainly in terms of initial higher demerit points for fishy odour, gills and eyes; however, no effect was observed in the cooked fillets. Copyright © 2004 Society of Chemical Industry     

Comparison of Whole with Headed and Gutted Orange Roughy Stored in Ice: Sensory, Microbiology and Chemical Assessment

Sensory, microbiological and chemical analyses were used to compare whole orange roughy stored in ice with headed and gutted orange roughy stored in ice. Sensory results indicated that the whole fish had a shelf-life of 11 to 13 days. Heading and gutting gave only a slight increase in storage life. Microbiological results suggested that this increase was not due to any reduction in bacterial activity. However, chemical analyses indicated that there was reduced autolysis in the headed and gutted fish. Sulfide producing bacteria were not a significant proportion of the spoilage flora. The K value and results of analyses of inosine 5′-monophosphate and inosine were consistent with the sensory results and therefore these chemical tests are considered useful for monitoring changes in the freshness of orange roughy during ice storage.     

Strength of Gels Prepared from Washed and Unwashed Minces of Hoki (Macruronus novaezelandiae) Stored in Ice

Washed and unwashed fish minces were prepared from hoki that had been stored in ice. Gels were formed from the minces, cooked at both 60°C and 90°C and assessed by puncture, torsion and a folding test method. The strength of the gels decreased as the fish were stored. However, after 10 days, the strength of gels made from hoki minces still compared favorably with gels made from other commercial fish species without storage. This suggests that manufacture of hoki surimi on-shore may be practical. Fish freshness as evaluated by sensory methods was closely related to the K value and gel strength. Hence K values might provide the basis of a raw material quality control system for an on-shore surimi plant.     

Comparison of Shelf Life and Quality of Mullet Stored at Zero and Subzero Temperature

The shelf life and quality of mullet (Mugil spp.) caught off the Southeast Atlantic coast were evaluated during storage at subzero temperature (-2°C) either unpackaged or vacuum packed in iolon film. Subzero temperature was maintained by storing fish in either 2% NaCl- or 7% propylene glycol-ice. Shelf life of fish stored in -2°C ice was 10 days, compared to 7 days for the fish stored in 0°C ice. Extension of shelf life was attributed to delayed microbial growth and slow biochemical changes. Structural changes due to ice crystals at subzero temperature storage appeared to be minor compared to those which occurred during freezing at -20°C as revealed by microscopic examination. The minor structural changes along with insignificant biochemical changes resulted in products having acceptable eating quality for 10 days.     

不同前期储藏条件对鲢鱼烹饪特性的影响

研究了不同的前期储藏处理对鲢鱼烹制品质的作用。鲢鱼块在冷藏(-1℃)和冻藏(-20℃)条件下储藏0、3、6、9、12d后进行烹制处理,从化学、物理及感官方面评价储藏温度及时间对烹制后鲢鱼品质的影响。试验结果表明,烹制处理提高了鲢鱼肉的NPN、TVB-N及TMA含量;随储藏时间的延长,冷藏和冻藏的鲢鱼经烹制处理后鱼肉中总氮含量呈逐渐降低趋势,而非蛋白氮(NPN)、挥发性盐基氮(TVB-N)和三甲胺(TMA)含量均呈逐渐增加趋势,冷藏比冻藏的变化趋势显著。储藏时间越长,烹制后鱼肉组织质量劣化越严重。冷藏条件下适宜储藏时间不超过9d,也可延长至12d,且前期冻藏有利于保证鲢鱼肉烹制后的品质。     

Influence of ice storage on ray (raja clavata) wing muscle

Determinations of pH, urea, extractable protein (EP), apparent viscosity (AV), water-binding capacity (WBC), hardness (H), Hunter L, a and b values and sensory evaluation (SE) (raw and cooked), as well as microbiological analysis, were used to study the effects of ice storage on the stability of ray (Raja clavata) muscle. Significant changes were found in pH, bacterial growth and sensory assessment (ammoniacal odour and colour) during the storage period. Urea content, EP, AP, WBC (measured as water loss) and Hunter L value (in cooked muscle) decreased significantly. Statistical analyses did not show significant differences in H and Hunter L value (in raw muscle). The decrease in urea concentration can be described as a linear function of the number of microorganisms suggesting the microbiological character of the process. No dependence was observed between pH or number of microorganisms and EP, whereas AP was much more affected and showed a marked dependence on these two parameters treated independently. The results of this research showed that wings could be stored in ice for 9–10 days without causing important loss of quality. The fish was considered excellent up to day 7 and acceptable after 9 days but unacceptable after 11–12 days onwards. Nonetheless, the shelf-life of the ray in the iced state can vary depending upon the initial state of freshness, handling and the biological conditions of the fish. Microbiological analysis, pH, EP, AV, WBC, SE and Hunter L value have been demonstrated to be factors which could be used to monitor the deterioration of ray during ice storage.     

Use of electrolyzed water ice for preserving freshness of pacific saury (Cololabis saira)

The effects of electrolyzed water ice (EW-ice), compared with traditional tap water ice (TW-ice), on the microbiological, chemical, and sensory quality of Pacific saury (Cololabis saira) stored for a period of up to 30 days at 4 degrees C were evaluated. EW-ice with active chlorine at a concentration of 34 mg/kg was prepared from weak acidic electrolyzed water, whose pH, oxidation-reduction potential, and chlorine content were 5, 866 mV, and 47 mg/liter, respectively. Microbiological analysis showed that EW-ice, compared with TW-ice, markedly inhibited the growth of both aerobic and psychrotrophic bacteria in saury flesh during refrigerated storage, primarily because of the action of active chlorine. Chemical analysis revealed that EW-ice retarded the formation of volatile basic nitrogen and thiobarbituric acid-reactive substances and reduced the accumulation of alkaline compounds in the fish flesh in comparison with TW-ice. Sensory analysis confirmed that the freshness of saury was better preserved in EW-ice than in TW-ice and showed that the saury stored in EW-ice had a shelf life that was about 4 to 5 days longer than the fish stored in TW-ice.     

Aerobic Counts, Color and Adenine Nucleotide Changes in CO2 Packed Refrigerated Striped Bass Strips

Hybrid striped bass (HSB) strips were dipped in chlorine or distilled water and packaged in 60% CO₂, 6% O₂, and 34% N₂ (MAP) or in AIR. APC reached 10⁸ CFU/g after 4 days for AIR and 10 days for MAP fish. Sensory panelists detected a whiter color flesh in fish treated with chlorine. Hypoxanthine increased while IMP decreased and ADP and ATP did not change throughout. If inosine was excluded in the predictor, a modified K value (K*) could be applicable as a freshness indicator of freshwater HSB but storage environment should be specified. K* values correlated highly with APC for AIR (R²= 0.84) and MAP packs (R²= 0.85).     

Bulk preservation of small pelagic fish by gamma irradiation: studies on a model storage system using Anchovies

Non-packaged, whole anchovy (Stolephorus commersonii) in lots of 20 kg were subjected to gamma irradiation at 2 kGy. The treated fish were stored under ice in insulated boxes which were held at 13°C. The slow melting of the ice under the storage conditions continuously washed the fish during storage. At periodic intervals, quality of the fish was determined by sensory, chemical and microbiological parameters. The non-packaged irradiated fish had better quality attributes which was acceptable up to 17 days in comparison to a storage life of 13 days for the unirradiated counterpart. Although packaged irradiated fish had a longer shelf life of 20 days, packaging caused drip accumulation and poor appearance of the fish. The advantages of the non-packaged storage system in commercial handling of irradiated small pelagic fish species are discussed.     

Freshness assessment of cultured sea bream (Sparus aurata) by chemical,physical and sensory methods

The quality changes of cultured sea bream (Sparus aurata) stored in ice for a period of up to 23 days were determined by K and related values, sensory assessment and texture by texturometer. Sensory schemes, based on the Tasmanian Food Research Unit (TFRU) scheme for raw fish and on the Torry scheme for cooked fish were modified to be appropriate for whole cultured sea bream, according to the trained panellists’ perceptions, during the storage period in ice. The TFRU sensory score of fish showed good agreement with K value and texture results throughout the storage period. The limit for acceptability of cultured sea bream stored in ice was about 17–18 days. Generally, K, K_i and G values had good correlation with the degree of freshness and can be used as freshness indicators.     

流化冰对养殖大黄鱼保鲜效果的研究

为探究流化冰对养殖大黄鱼的保鲜效果和应用可行性,研究流化冰的预冷效果及大黄鱼在贮藏过程中感官品质、质构特性、微生物和化学指标的变化情况.结果表明,流化冰(-1℃)将大黄鱼冷却至0.3 ℃需42 min,较碎冰(4 ℃)组冷却至相同温度缩短了65％.在整个贮藏期内,流化冰组大黄鱼的感官评分、硬度和弹性均优于同期的对照组,...     

紫苏水提物联合蒸煮处理对脆肉鲩鱼片冻藏过程中品质的影响

为了研究蒸煮处理及紫苏水提物对脆肉鲩鱼片冻藏品质的影响,以紫苏水提物浸泡的生鱼片（生鱼片组）、紫苏水提物浸泡再进行蒸煮制备的熟鱼片（熟鱼片组）、蒸馏水浸泡的生鱼片（对照组）为研究对象,研究这3 组鱼片在冻藏过程中质构、持水性、盐溶性蛋白含量、Ca2＋-ATPase活性、硫代巴比妥酸（thiobarbituric acid,TBA）值、挥发性盐基氮（total volatile base-nitrogen,TVB-N）含量和感官评分的变化。结果表明：熟鱼片及生鱼片组通过最大冰晶生成带的时间比对照组长;与对照组和生鱼片相比,熟鱼片在冻藏过程中一直维持较高的硬度、弹性、咀嚼性、TBA值和较低的持水力、盐溶性蛋白含量、TVB-N含量;与对照组相比,生鱼片组的质构特性、持水力、盐溶性蛋白含量和Ca2＋-ATPase活力更高,而TBA值和TVB-N含量更低,冻藏300 d后,生鱼片TBA值是贮藏初始时的3.85 倍,TVB-N含量低于20 mg/100 g;感官评价结果进一步表明,3 组样品感官品质在冻藏过程中不断下降,其质地、口感以及汤汁浑浊度评分从高到低依次是熟鱼片、生鱼片和对照组。研究结果证明了紫苏水提物联合蒸煮处理更有利于冻藏过程中脆肉鲩鱼片品质的维持。     

Nucleotide Catabolism: Influence on the Storage Life of Tropical Species of Fish from the North West Shelf of Australia

The storage life of four species of fish from the North West Shelf was examined by means of nucleotide catabolism and sensory evaluation. It was found that the shelf life was related to the rate of inosine monophosphate (IMP) breakdown rather than to bacterial spoilage, because the endemic mesophilic bacteria were unable to adapt to ice storage conditions. The results indicated that the IMP level was fundamentally related to both flavor intensity, and acceptability, and was not merely circumstantially related to time of storage.     

鲤鱼鱼鳞蛋白酶解液对鲤鱼肉冷藏期间品质变化的影响

为研究鲤鱼鱼鳞蛋白酶解液对鲤鱼肉冷藏期间品质的影响,本文以新鲜鲤鱼肉为研究对象,将鱼肉分别在不同浓度鲤鱼鱼鳞蛋白酶解液(0.01、0.03、0.04 g/mL)作浸渍处理(无菌水浸渍处理为对照组),置于4 ℃条件下贮藏,在0、2、4、6、8、10 d进行各组样品的菌落总数、可溶性蛋白含量、蒸煮损失率、汁液流失率、硫代巴比妥酸(thiobarbituric acid,TBA)值、酸价、总巯基与游离巯基含量等指标测定。结果得出,经鲤鱼鱼鳞蛋白酶解液处理后鲤鱼肉样品,各浓度处理组的总巯基与可溶性蛋白含量的降幅均缓于对照组,且游离巯基含量、TBA值、汁液流失率、蒸煮损失率与酸价值的增幅不大。其中,对照组样品在第6 d时的菌落总数超过二级鲜度,而处理组样品在第10 d时仍处在二级鲜度(4.01~6.01lg CFU/g)。并且0.03 g/mL鲤鱼鱼鳞蛋白酶解液的处理效果最佳,使鲤鱼鱼肉的保藏期延长4 d。说明鲤鱼鱼鳞蛋白酶解液能有效减缓鲤鱼肉冷藏期间的脂肪与蛋白质氧化。     

黄原胶对冷冻熟面冻藏品质的影响

研究添加黄原胶对冷冻熟面质构特性和蒸煮品质的影响,并采用差示扫描量热仪(DSC)和低场核磁共振(NMR)探究了添加黄原胶对冷冻熟面冻藏过程中可冻结水含量和水分分布的影响;利用激光共聚焦显微镜(CLSM)观察了冻藏过程中蛋白质网络结构的变化。结果表明:添加黄原胶可以提高冷冻熟面的硬度、咀嚼性和拉伸性能,降低复煮损失率和吸水率,减缓在冻藏过程中质构品质和蒸煮品质的降低趋势。黄原胶的加入可以使冻藏过程中冷冻熟面的蛋白质网络结构更加连续致密,抑制深层结合水向弱结合水方向的转移,减少可冻结水的含量,从而减少冰晶的形成,减轻因冰晶带来的机械损伤,从而改善冷冻熟面的冻藏品质。